The polymerization of monomers, which contain acrylic groups, in the form of water-in-oil emulsion, is known from the prior art. Dispersions are obtained, the particle size of which generally is larger than 300 nm. At the same time, the particles have a relatively broad spectrum of particle sizes.
The following publications are referred to as being representative of the extensive prior art:
In the "Journal de chimie physique", 1981, volume 78, number 3, Y. S. Leong, G. Riess and F. Candau, using an oil-soluble free radical-forming material, report the photopolymerization of acrylamide into a water-in-oil emulsion. The reaction is carried out in the presence of a polystyrene-polyoxyalkylene block copolymer as stabilizer and propanol in toluene-water mixtures. The latexes obtained are transparent and, as confirmed by dialysis experiments, consist of micellar solutions swollen in water. The molecular weight of the polyacrylamide obtained falls within the range of 50,000 to 130,000.
From the "Colloid Polym. Sci.", 264 (7), 616, the synthesis of poly(vinyl acetate) and poly(methyl methacrylate) in the form of particles with a diameter of 100 to 300 nm is known by the dispersion polymerization in a nonaqueous medium in the presence of polystyrene-polyoxyalkylene copolymers. For this synthesis, the particle diameter decreases as the concentration of block copolymer increases.
The British patent 2,140,433 discloses the preparation of stable water-in-oil emulsions with a high polymer content and a low viscosity by a free radical polymerization by the addition of the aqueous solution of a water-soluble monomer, such as acrylic acid, to an inert, hydrophobic, organic liquid.
U.S. Pat. No. 3,284,393 relates to a method, in which water-soluble monomers, such as acrylic acid, methacrylic acid, acrylamide and other monomers in aqueous solution are emulsified in a water-immiscible oil in the presence of a low molecular weight emulsifier, such as sorbitol monooleate, and a buffer. The polymerization is carried out with oil-soluble free radical initiators. Polymer particles with a diameter of about 100 nm are obtained at a reaction temperature of 60.degree. C. in the course of a reaction requiring 48 hours for completion.